Many rubber articles, such as tires, incorporate text, aesthetic designs, and other visual effects on the article's surface. Such elements may be used to convey information about the brand, style, type, size, performance, rating, and intended operating conditions of the article. Such elements may also be directed toward making the article more visually appealing to a purchaser or user of the product. Many rubber articles, such as tires, are comprised of solid black materials that offer very little in the way of contrast in the surface of the rubber article.
The elements noted above are made up of either indentations (e.g. concave portions) or protrusions (e.g., convex portions) in the surface of the rubber article. Emphasis of a particular article is achieved by increasing the depth or height of the indentation or protrusion, respectively. A rubber article is typically molded under high pressures and temperatures inside of a mold, requiring sophisticated venting at the mold-rubber interface to ensure that the rubber fully contacts the mold where intended, especially at or around mold elements intended to create indentations or protrusions. The site of a protrusion or indentation in a rubber article often generates a stress riser in the article, resulting in a potential weak point that may necessitate use of additional, thicker material to overcome.
Use of additional or thicker material to overcome stress risers in rubber articles results in a rubber article that is heavier than necessary, and which requires more material than is otherwise necessary. Improved methods and apparatuses are needed for creating visual effects on a rubber article.